Vacuum-operable units for use with ignition distributors

ABSTRACT

A vacuum-operable unit for use with an ignition distributor includes a casing which is divided into first and second chambers by a diaphragm. A plunger is slidably received in the first chamber, and is connected at one end to the diaphragm, and extends at its other end from the first chamber for connection to the distributor, so that axial movement of the plunger varies the ignition timing of the distributor. The first chamber is vented to atmosphere, and the second chamber includes a conduit through which vacuum can be applied to the second chamber. A spring arrangement acts on the diaphragm to urge the diaphragm from a first position wherein, in use, the ignition timing of the distributor is advanced, to a second position wherein the ignition timing of the distributor is in a minimum advance position for normal operation. The spring arrangement is capable of urging the diaphragm from the second position to a third position wherein the ignition timing of the distributor is retarded beyond the minimum advance position, when opposite sides of the diaphragm are subject to equal pressures.

United States Patent [72] Inventor Willhm Harold Cooltsey Walsall, England [21] Appl. No. 847,254 [22] Filed Aug. 4,1969 [45] Patented Aug. 24, 1971 [73] Assignee Joseph Lucas (Industries) Limited 3 l [32] Priority Aug. 12, 1968 [33] Great Britain 38426/68 [54] VACUUM-OPERABLE UNITS FOR USE WITH IGNITION DISTRIBUTORS 4 Claims, 2 Drawing Figs. [52] US. Cl. 123/117 A [51] Int. Cl. F02p 5/10 [50] Fie1do1Search..... 123/117, 1 17.1

[56] References Cited UNITED STATES PATENTS 2,087,339 7/1937 Arthur 123/1 17.1 2,473,805 6/1949 Mallory 123/1 17.1

Primary ExaminerMark M. Newman Assistant Examiner-Cort R. Flint Attorney-Holman & Stern ABSTRACT: A vacuum-operable unit for use with an ignition distributor includes a casing which is divided into first and second chambers by a diaphragm. A plunger is slidably received in the first chamber, and is connected at one end to the diaphragm, and extends at its other end from the first chamber for connection to the distributor, so that axial movement of the plunger varies the ignition timing of the distributor. The first chamber is vented to atmosphere, and the second chamber includes a conduit through which vacuum can be applied to the second chamber. A spring arrangement acts on the diaphragm to urge the diaphragm from a first position wherein, in use, the ignition timing of the distributor is ad vanced, to a second position wherein the ignition timing of the distributor is in a minimum advance position for normal operation. The spring arrangement is capable of urging the diaphragm from the second position to a third position wherein the ignition timing of the distributor is retarded beyond the minimum advance position, when opposite sides of the diaphragm are subject to equal pressures.

PATENTED mmzmn 3.601.105

ATT ENEYS PATENTED AUBZMB'H 3,501 105 sum 2 OF 2 A ll/lI/1 INVENTOE Mam C E Y%%I ATTSENEYS VACUUM-OPERABLE UNITS FOR USE WITH IGNITION DISTRIBUTORS It is known that if an internal combustion engine in a road vehicle is functioning with the throttle valve of its carburetor substantially closed, for example in overrun or idling conditions, there is incomplete combustion of the fuel in the cylinders of the engine, resulting in the formation of a high percentage of noxious products including unbumt hydrocarbons in the exhaust emission of the vehicle. It has been proposed to reduce the formation of such noxious products, in closed throttle conditions, by providing an air supply to the cylinders of the engine, even though the throttle is closed, to enable complete combustion of the fuel which is present to take place/However, this procedure, although providing a reduction in the emission of noxious products, causes an increase in the engine speed and consequential loss of engine braking in the overrun condition. I

It has been found, however, that by retarding the ignition timing of the engine beyond the normal setting for closed throttle conditions, the loss in engine braking is minimized and it is an object of the present invention to provide a vacuumoperable unit for connection to the distributor of the engine whereby such an adjustment of the ignition timing can be made automatically at closed throttle conditions.

According to the invention a vacuum-operable unit for use with an ignition distributor includes a casing, a diaphragm dividing the easing into first and second chambers, a plunger slidably received in the first chamber, the plunger being secured at one end to the diaphragm and extending at its other end from the first chamber for connection to the distributor, so that axial movement of the plunger varies the ignition timing of the distributor, a vent in the wall of the first chamber opening the first chamber to atmosphere, a conduit communicating with the second chamber and through which vacuum can be applied to the second chamber, and a spring arrangement urging the diaphragm from a first position wherein in use the ignition timing of said distributor is advanced to a second position wherein the ignition timing of the distributor is in a minimum advance position for normal operation, and capable of urging the diaphragm from said second position to a third position wherein the ignition timing of the distributor is retarded beyond said minimum advance position, when opposite sides of the diaphragm are subject to equal pressures.

' The invention further resides in an ignition distributor for a road vehicle, having combined therewith a unit as specified in the preceding paragraph.

The invention still further resides in an ignition timing control system for a road vehicle utilizing an ignition distributor as specified in the preceding paragraph.

One example of the invention is illustrated in the accompanying drawings wherein FIG. 1 is a sectional view of a vacuum unit, and

FIG. 2 is a diagrammatic representation of an ignition control system utilizing the unit shown in FIG. 1.

Referring to the drawing, there is provided a vacuum unit 11 adapted to be mounted on the casing of an ignition distributor mounted in turn on the engine of a road vehicle. The vacuum unit 11 includes a casing 12 formed in two parts 12a, 12b respectively, a diaphragm 13 being trapped between the two parts, and dividing the interior of the easing into first and second chambers 14, 15 respectively. The part 12a of the easing includes an axially extending hollow spigot 16, which includes a portion 16a which extends into the chamber 14. The casing part 12b also includes a hollow spigot 17, and moreover the wall of the casing part 121; includes a conduit 18 which communicates with the chamber 15. Secured to the spigot 16 and extending axially therefrom is a mounting rod which is screw threaded at its end remote from he spigot 16. The vacuum unit is mounted on the casing 30 (FIG. 2) of an ignition distributor, with the spigot 16 slidably received in a passage; in the wall of the casing of the distributor, and the rod 19 engaged with a captive nut which is rotatable to vary the position of the vacuum unit relative to the distributor. A push rod 21 extends axially within the spigot 16, and projects from the end thereof remote from the diaphragm. One end of the rod 21 extends through the diaphragm, and the rod 21 is formed with a pair of flanges 22, 23 which trap a pair of washers 24, 25 against opposite sides of the diaphragm 13. Thus, the rod 21 moves with the diaphragm 13. At its end remote from the diaphragm 13, the rod 21 is connected to the movable timing plate 30a of the ignition distributor, so that as the rod 21 moves the timing plate 30a of the distributor is moved to vary the ignition timing of the distributor. A vent is provided around the rod 21 so that the chamber 14 is open to atmosphere.

Secured to the inner surface of the casing part 12b, and partially closing the hollow spigot 17 is an annular plate 26, the wall of the central hole of which is extended to define a tubular member 27 extending towards the diaphragm 13. Slidably mounted within the tubular member 27 is a metal cup 28, the base of which is provided with a hole 29 through which the end of the push rod 21 can project. At its opposite end the cup 28 is formed with an outwardly extending peripheral flange 31 of larger diameter than the diameter of the tubular member 27. Positioned within the cup 27, is a further elongated metal cup 32 which is provided at its open end, adjacent the base of the cup 28 with an outwardly directed peripheral flange 33 of larger diameter than the diameter of the hole 29 in the base of the cup 28. The end of the push rod 21 projects into the cup 32, and acting between the flange 23 on the rod 21 and the closed end of the cup 32 is a relatively weak compression spring 34. A relatively strong compression. spring 35 acts between the closed end of the spigot 17 of the casing part 12b and the flange 33 of the cup 32, the spring 35 surrounding the cup 32 and urging the cup 32 and the cup 28 towards the diaphragm 13, under the action of the spring 35, is limited by engagement of the flange 31 of the cup 28 with the plate 26.

When both the chamber 14 and the chamber 15 are at atmospheric pressure, than the weak spring 34 urges the diaphragm 13 to the left as shown in the drawings, until the washer 24 engages the end of the portion 16a of the spigot 16. As soon as vacuum is applied to the chamber 15, atmospheric pressure in the chamber 14 overcomes the spring 34 and the diaphragm moves to the position shown in v the drawing, wherein the washer 25 engages the base ofthe cup 28. As the vacuum in the chamber 15 strengthens, the pressure gradient between the chambers 14, 15 increases sufficiently for the diaphragm to move further to the right thereby sliding the cup 28 to the right with respect to the plate 26 against the action of the strong spring 35.

All movements of the diaphragm 13 are followed by the rod 21, and when the diaphragm is in the position shown in the drawings, then the ignition timing of the ignition distributor is in a predetermined minimum advance condition. Movement of the diaphragm to the right from the position shown advances the ignition timing, and movement of the diaphragm to the left of the position shown retards the ignition timing.

An ignition control system for the engine of a road vehicle utilizing the vacuum unit 11 operates in the following manner. The vacuum unit 11 is mounted on the casing 30 of the ignition distributor of the vehicle in the manner described above, and the conduit 18 is connected to the outlet 37 of a two position spool valve 36. The spool valve 36 includes a chamber 38 having, in addition to the outlet 37, a pair of spaced inlets 39, 41, slidable in the chamber 38 is a spool 42 which is movable in response to movement of the throttle pedal of the rear vehicle, between a first position wherein the outlet 37 communicates with the inlet 39 and the inlet 41 is closed and a second position wherein the outlet 37 communicates with the inlet 41 and the inlet 39 is closed. The inlet 41 is open to atmosphere and the inlet 39 communicates with the inlet manifold 43 of the engine 40 of the vehicle, downstream of the throttle valve 44 of the carburetor of the engine, or is connected in any other suitable position to provide the desired characteristics. Thus, when the spool 42 is in its first position, the chamber 15 of the unit 11 is subject to the pressure conditions existing in the manifold of the engine, while when the spool valve is in its second position the chamber 15 is open to atmosphere. Means (not shown) is provided for admitting air to the engine 40 during closed throttle conditions to allow complete combustion of fuel entering the cylinders of the engine.

As previously stated, the spool 42 is movable in response to movements of the throttle pedal of the vehicle, and the arrangement is such that when the throttle valve 44 of the carburetor of the engine is closed, that is to say in overrun or idling conditions of the engine, then the spool 42 is in its second position, the spool being moved to its first position immediately the throttle pedal of the vehicle is operated to open the throttle valve 44. Thus, when the engine 40 is operating in an idling, or in an overrun condition, the throttle valve 44 is closed, and the spool 42 is in its second position so that the chamber 15 is open to atmosphere. Since the chamber 15 is open to atmosphere the air pressures acting on opposite sides of the diaphragm 13, are equal, and so the diaphragm l3, and consequently the push rod 21 will be moved to the left under the action of the spring 34, thereby retarding the ignition timing of the engine, and compensating for the increase in engine speed resulting from the admission of extra air into the cylinders of the engine to allow complete combustion of the fuel entering the cylinders in the closed throttle valve condition. Immediately the throttle pedal is operated to open the throttle valve 44, the overrun, or idling condition no longer exists, and so the retardation of the ignition timing is not required. Thus, as the throttle pedal is operated the spool 42 is moved to its first position to establish communication between the inlet manifold 43 of the engine and the chamber 15. While the engine of the vehicle is running, the air pressure in the inlet manifold of the engine is always at least slightly below the ambient atmospheric pressure, and so when the spool 42 is in its first position a pressure gradient exists between the chambers 14, 15. The strength of the spring 34 is such that the minimum pressure gradient which occurs between the chambers l4, 15 when the spool 42 is in its first position, is sufficient to overcome the action of the spring 34, and to return the diaphragm to the minimum advance position shown. Thereafter as the engine of the vehicle is accelerated, the ignition timing of the engine is advanced from the minimum advanced condition, the diaphragm, and consequently the rod 21 moving to the right (as shown in the drawing) against the action of the spring 35 to control advancement of the ignition timing from, and retardation of the ignition timing to, the minimum advanced condi: tion. it will be appreciated that during compression of the spring 35 the spring 34 plays no part, and is carried with the cup 32.

The spool 42 of the valve 36 can be operated by the throttle pedal of the road vehicle mechanically, hydraulically or electrically, or can be operated in response to variations in the inlet manifold depression, it being appreciated that variations in the inlet manifold depression are dependent upon the position of the throttle pedal.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A vacuum-operable unit, for use with an ignition distributor, including a casing, a diaphragm dividing the casing into first and second chambers, a plunger slidably received in the first chamber, the plunger being secured at one end to the diaphragm and extending at its other end from the first chamber for connection to the distributor, so that axial movement of the plunger varies the ignition timing of the distributor, a vent in the wall of the first chamber opening the first chamber to atmosphere, a conduitcommunicating with the second chamber, and through which vacuum can be applied to the second chamber, a first spring urging the diaphragm from a first position wherein in use theignition timing of the distributor is advanced, to a second position wherein the ignition timing of the distributor is in a minimum advanced position for normal operation, and a second spring urging the diaphragm from second position to a third osition wherein the ignition timing of the distributor is retar ed beyond said minimum advance position, when opposite sides of the diaphragm are subject to equal pressures, the second spring moving bodily with the diaphragm during the movement of the diaphragm between the first and second positions.

2. An ignition distributor including a vacuum-operable unit as claimed in claim 1, said unit being carried by the casing of the distributor with said plunger connected to a movable timing arrangement of the distributor, so that axial movement of the plunger alters the ignition timing of the distributor.

3. An ignition distributor as claimed in claim 2, wherein said vacuum-operable unit is adjustably mounted on the casing of the distributor.

4. An ignition turning control system for a road vehicle, including an ignition distributor as claimed in claim 3, and a two position control valve operable in response to movement of the throttle pedal of the vehicle, said control valve having a first position which it occupies when the throttle pedal is in a closed throttle position and in which it connects said second chamber of the vacuum unit to atmosphere so that the ignition timing of the distributor is retarded beyond said minimum advance position, and a second position which it occupies when the throttle pedal is in an open throttle position and in which the control valve connects said second chamber of the vacuum unit to the inlet manifold of the engine of the vehicle so that the ignition timing of the distributor is advanced from and retarded to aid minimum advance position in accordance with the pressure conditions in the inlet manifold of the engine. 

1. A vacuum-operable unit, for use with an ignition distributor, including a casing, a diaphragm dividing the casing into first and second chambers, a plunger slidably received in the first chamber, the plunger being secured at one end to the diaphragm and extending at its other end from the first chamber for connection to the distributor, so that axial movement of the plunger varies the ignition timing of the distributor, a vent in the wall of the first chamber opening the first chamber to atmosphere, a conduit communicating with the second chamber, and through which vacuum can be applied to the second chamber, a first spring urging the diaphragm from a first position wherein in use the ignition timing of the distributor is advanced, to a second position wherein the ignition timing of the distributor is in a minimum advanced position for normal operation, and a second spring urging the diaphragm from said second position to a third position wherein the ignition timing of the distributor is retarded beyond said minimum advance position, when opposite sides of the diaphragm are subject to equal pressures, the second spring moving bodily with the diaphragm during the movement of the diaphragm between the first and second positions.
 2. An ignition distributor including a vacuum-operable unit as claimed in claim 1, said unit being carried by the casing of the distributor with said plunger connected to a movable timing arrangement of the distributor, so that axial movement of the plunger alters the ignition timing of the distributor.
 3. An ignition distributor as claimed in claim 2, wherein said vacuum-operable unit is adjustably mounted on the casing of the distributor.
 4. An ignition turning control system for a road vehicle, including an ignition distributor as claimed in claim 3, and a two position control valve operable in response to movement of the throttle pedal of the vehicle, said control valve having a first position which it occupies when the throttle pedal is in a closed throttle position and in which it connects said second chamber of the vacuum unit to atmosphere so that the ignition timing of the distributor is retarded beyond said minimum advance position, and a second position which it occupies when the throttle pedal is in an open throttle position and in which the control valve connects said second chamber of the vacuum unit to the inlet manifold of the engine of the vehicle so that the ignition timing of the distributor is advanced from and retarded to aid minimum advance position iN accordance with the pressure conditions in the inlet manifold of the engine. 